CA2186228C - Method of making liquid crystal composite - Google Patents
Method of making liquid crystal composite Download PDFInfo
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- CA2186228C CA2186228C CA002186228A CA2186228A CA2186228C CA 2186228 C CA2186228 C CA 2186228C CA 002186228 A CA002186228 A CA 002186228A CA 2186228 A CA2186228 A CA 2186228A CA 2186228 C CA2186228 C CA 2186228C
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- liquid crystal
- crystal material
- encapsulating
- matrix
- refraction
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/52—Liquid crystal materials characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
- C09K19/54—Additives having no specific mesophase characterised by their chemical composition
- C09K19/542—Macromolecular compounds
- C09K19/544—Macromolecular compounds as dispersing or encapsulating medium around the liquid crystal
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
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- Crystallography & Structural Chemistry (AREA)
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- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
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Abstract
A method is described for making a liquid crystal composite in which droplets of a liquid crystal material are dispersed in a matrix material. An encapsulating material at least partially separates the liquid crystal from the matrix material. This construction permits the matrix material to be selected on the basis of its processing and environmental properties and the encapsulating material to be selected on the basis of its emulsifying ability and orientational interactions with liquid crystal material. Light valves made from such a composite exhibit improved electro-optical properties.
Description
.-METHOD OF MAKING LIQUID CRYSTAL COMPOSTTE
This invention relates to liquid crystal composites suitable for use in light valves and methods of making the same.
s Backgtound of the Inven~on Liquid crystal light valves in which the electro-optically active element is a liquid crystal composite in which plural volumes or droplets of a liquid crystal material are dispersed, encapsulated, embedded, or otherwise contained within a matrix material such as a polymer are known. Exemplary disclosures io include Fergason, US 4,435,047 (1984) ('Fergason '047"); West et al., US
4,685,771 (1987); Pearlman, US 4,992,201 (1991); Dainippon Ink, EP 0,313,053 (1989).
These light valves may be used in displays and window or privacy panels.
is The prior art also discloses the concept of having a further material disposed between the matrix material and the liquid crystal material. See, for example, Fergason, '047; Fergason et al., US 4,950,052 (I990) ("Fergason '052");
and Raychem, WO 93!18431 (1993) (°Raychem '431'7. The purpose of having this fiuther material has been variously stated as preserving the integrity of the Zo volumes of liquid crystal material and for altering the electro-optical properties of the composite.
However, the techniques disclosed for forming a composite with this intervening further material have been specialized and are not generally 2s applicable to a wide variety of materials. The present invention provides an improved process for maiang such composites, which is more generally applicable than those disclosed in the prior art.
There is provided a method for making a liquid crystal composite wherein 3o plural volumes of a liquid crystal material are dispersed in a matriz material and the liquid crystal material is at least partially separated from the matxix material by an encapsulating material disposed therebetween, which method comprises the steps of _I_ PC'TiL~S9~i036~6 (a) emulsifying a combination of the liquid crystal material, the encapsulating material, and a carrier medium to form an emulsion in which capsules comprising a volume of liquid crystal material contained within the encapsulating material are suspended in the carrier medium;
s (b) separating the capsules from the Garner medium;
(c) dispersing the capsules in a medium in which the matrix material or a precursor thereof is present; and (d) causing the matrix material or precursor thereof to set around the capsules, to form the liquid crystal composite.
to Brief Descrit~tion of the Drawin~(s) Fig. 1a-lb show a prior light valve made from a liquid crystal composite.
Fig. 2a-2b show a light valve made from a liquid crystal composite made according to the present invention.
Fig. 3 shows the contrast performance of various devices made according to this invention as a function of temperature.
Fig. 4 shows the operating voltage as a function of temperature for various 2o devices made according to this invention as a function of temperature.
Fig. la shows a prior art light valve made from a liquid crystal composite, such as described in Fergason '047. Light valve 10 comprises a liquid crystal composite 11 in which droplets or volumes 12 of nematic liquid crystal material 13 having a positive dielectric anisotropy are dispersed in a matrix material 14.
Composite lI is sandwiched between first and second electrodes 15a and 15b, made firom a transparent conductor such as indium tin o~dde ("ITO"). The application or not of a voltage across electrodes 15a and 15b from power source 16 is controlled by switch 17, shown here in the open position ("off state"). As a ao result, no voltage is impressed across composite 11 and the electric field experienced by liquid crystal material 13 is effectively zero. Due to surface interactions, the liquid crystal molecules preferentially lie with their long axes parallel to the curved interface with matriz material 14, resulting in a generally curvilinear alignment within each droplet. The curvilinear saes in different droplets 12 are randomly oriented, as symbolized by the differing orientations of WO 951Z~?'.8 PCT;'I:S9~10365G
the curvilinear patterns. Liquid crystal material 13 has an extraordinary index of refraction ne which is different from the index of refraction nn, of matrix material 14 and an ordinary index of refraction no which is the substantially the same as nm. (Herein, two indices or refraction as said to be substantially the s same, or matched, if they differ by less than 0.05, preferably less than 0.02.) Incident light ray 18 traveling through composite 11 has a high statistical probability of encountering at least one interface between matrix material 14 and liquid crystal material 13 in which the liquid crystal index of refraction with which it operatively interacts is ne. Since ne is different from nm, there is io refraction, or scattering of light ray 18, both forwardly and backwardly, causing composite 11 to have a translucent or frosty appearance..
Fig. lb shows light valve 10 in the on-state, with switch 17 closed. An electric field is applied between electrodes 15a and 15b and across composite 11, is with a directionality indicated by arrow 19. Liquid crystal material 13, being positively dielectrically anisotropic, aligns parallel to the electric field direction.
(The required voltage is dependent inter alia on the thickness of the composite and typically is between 3 and 50 volts.) Further, this alignment with the field occurs in each droplet 12, so that there is order among the directors from droplet 2o to droplet, as shown symbolically in Fig. lb. When the liquid crystal molecules are aligned in this manner, the liquid crystal index of refraction with which incident light ray 18 operatively interacts is no. Because no is substantially the same as na,, there is no scattering at the liquid crystal-matrix material interface. As a result, ray 18 is transmitted through composite 11, which now 2s appears transparent. Transmission rates of at least 50 96, and preferably on the order of 70 ~'v or higher, may be attained.
The electro-optical performance (e.g., switching voltage, off state scattering, switching speed, and hysteresis) of light valve 10 is dependent on the so nature of the surface interactions between matriz material 14 and liquid crystal material 13. A matriz material which is desirable in respect of characteristics such as mechanical propertses, ability to protect against environmental contaminants, ITV stability, etc. may be undesirable in respect of its surface interactions with the liquid crystal material, for example causing the switching 35 Speed to be too slow or the switching voltage to be too high. Thus, it is desirable to be able to divorce the surface interactions from the other characteristics of the matrix material.
This invention relates to liquid crystal composites suitable for use in light valves and methods of making the same.
s Backgtound of the Inven~on Liquid crystal light valves in which the electro-optically active element is a liquid crystal composite in which plural volumes or droplets of a liquid crystal material are dispersed, encapsulated, embedded, or otherwise contained within a matrix material such as a polymer are known. Exemplary disclosures io include Fergason, US 4,435,047 (1984) ('Fergason '047"); West et al., US
4,685,771 (1987); Pearlman, US 4,992,201 (1991); Dainippon Ink, EP 0,313,053 (1989).
These light valves may be used in displays and window or privacy panels.
is The prior art also discloses the concept of having a further material disposed between the matrix material and the liquid crystal material. See, for example, Fergason, '047; Fergason et al., US 4,950,052 (I990) ("Fergason '052");
and Raychem, WO 93!18431 (1993) (°Raychem '431'7. The purpose of having this fiuther material has been variously stated as preserving the integrity of the Zo volumes of liquid crystal material and for altering the electro-optical properties of the composite.
However, the techniques disclosed for forming a composite with this intervening further material have been specialized and are not generally 2s applicable to a wide variety of materials. The present invention provides an improved process for maiang such composites, which is more generally applicable than those disclosed in the prior art.
There is provided a method for making a liquid crystal composite wherein 3o plural volumes of a liquid crystal material are dispersed in a matriz material and the liquid crystal material is at least partially separated from the matxix material by an encapsulating material disposed therebetween, which method comprises the steps of _I_ PC'TiL~S9~i036~6 (a) emulsifying a combination of the liquid crystal material, the encapsulating material, and a carrier medium to form an emulsion in which capsules comprising a volume of liquid crystal material contained within the encapsulating material are suspended in the carrier medium;
s (b) separating the capsules from the Garner medium;
(c) dispersing the capsules in a medium in which the matrix material or a precursor thereof is present; and (d) causing the matrix material or precursor thereof to set around the capsules, to form the liquid crystal composite.
to Brief Descrit~tion of the Drawin~(s) Fig. 1a-lb show a prior light valve made from a liquid crystal composite.
Fig. 2a-2b show a light valve made from a liquid crystal composite made according to the present invention.
Fig. 3 shows the contrast performance of various devices made according to this invention as a function of temperature.
Fig. 4 shows the operating voltage as a function of temperature for various 2o devices made according to this invention as a function of temperature.
Fig. la shows a prior art light valve made from a liquid crystal composite, such as described in Fergason '047. Light valve 10 comprises a liquid crystal composite 11 in which droplets or volumes 12 of nematic liquid crystal material 13 having a positive dielectric anisotropy are dispersed in a matrix material 14.
Composite lI is sandwiched between first and second electrodes 15a and 15b, made firom a transparent conductor such as indium tin o~dde ("ITO"). The application or not of a voltage across electrodes 15a and 15b from power source 16 is controlled by switch 17, shown here in the open position ("off state"). As a ao result, no voltage is impressed across composite 11 and the electric field experienced by liquid crystal material 13 is effectively zero. Due to surface interactions, the liquid crystal molecules preferentially lie with their long axes parallel to the curved interface with matriz material 14, resulting in a generally curvilinear alignment within each droplet. The curvilinear saes in different droplets 12 are randomly oriented, as symbolized by the differing orientations of WO 951Z~?'.8 PCT;'I:S9~10365G
the curvilinear patterns. Liquid crystal material 13 has an extraordinary index of refraction ne which is different from the index of refraction nn, of matrix material 14 and an ordinary index of refraction no which is the substantially the same as nm. (Herein, two indices or refraction as said to be substantially the s same, or matched, if they differ by less than 0.05, preferably less than 0.02.) Incident light ray 18 traveling through composite 11 has a high statistical probability of encountering at least one interface between matrix material 14 and liquid crystal material 13 in which the liquid crystal index of refraction with which it operatively interacts is ne. Since ne is different from nm, there is io refraction, or scattering of light ray 18, both forwardly and backwardly, causing composite 11 to have a translucent or frosty appearance..
Fig. lb shows light valve 10 in the on-state, with switch 17 closed. An electric field is applied between electrodes 15a and 15b and across composite 11, is with a directionality indicated by arrow 19. Liquid crystal material 13, being positively dielectrically anisotropic, aligns parallel to the electric field direction.
(The required voltage is dependent inter alia on the thickness of the composite and typically is between 3 and 50 volts.) Further, this alignment with the field occurs in each droplet 12, so that there is order among the directors from droplet 2o to droplet, as shown symbolically in Fig. lb. When the liquid crystal molecules are aligned in this manner, the liquid crystal index of refraction with which incident light ray 18 operatively interacts is no. Because no is substantially the same as na,, there is no scattering at the liquid crystal-matrix material interface. As a result, ray 18 is transmitted through composite 11, which now 2s appears transparent. Transmission rates of at least 50 96, and preferably on the order of 70 ~'v or higher, may be attained.
The electro-optical performance (e.g., switching voltage, off state scattering, switching speed, and hysteresis) of light valve 10 is dependent on the so nature of the surface interactions between matriz material 14 and liquid crystal material 13. A matriz material which is desirable in respect of characteristics such as mechanical propertses, ability to protect against environmental contaminants, ITV stability, etc. may be undesirable in respect of its surface interactions with the liquid crystal material, for example causing the switching 35 Speed to be too slow or the switching voltage to be too high. Thus, it is desirable to be able to divorce the surface interactions from the other characteristics of the matrix material.
218 ~ 2 2 8 PC?/L,'S95/036~G
Fig. 2a-2b (where numerals repeated from Fig. la-b denote like elements) show a light valve 20 of this invention in which this objective is achieved.
Light valve 20 comprises a liquid crystal composite 21 which is similar to composite s of Fig. la-b, except that liquid crystal material 13 is separated from matrix material 14 by an encapsulating material 22. Light valve 20 appears frosty or translucent in the off state (Fig. 2a) and transparent in the on-state (Fig.
2b), for the reasons given above. The surface interactions affecting the alignment of liquid crystal material 13 are predominantly with encapsulating material 22 io and not with matrix material 14. Encapsulating material 22 may be selected on the basis of its interactions with liquid crystal material 13, while matrix material 14 may be selected on the basis of its mechanical, optical, or other properties. This way, the necessity to compromise in respect of one set or another of properties is avoided.
is Matching of n~ of the liquid crystal material with the index of refraction of the encapsulating material is important only if the thickness of the layer of encapsulating material is comparable to the wavelength of light. Generally the thickness is less than approaimatxly 100 nm, much less than the wavelengths of 20 400 to 700 nm for visible light, so that the matching of the indices of refraction is normally not necessary. However, where the layer of encapsulating material is thick or where minimizing of on-state haze is an objective (e.g., in window applications), matching of the indices of refraction is desirable. A colored visual effect may be obtained by inclusion of dyes, either pleochroic or isotropic, in the 25 liquid crystal material, In order to obtain the advantages of the present invention, it is not necessary that encapsulating material 22 completely separates matrix material 14 from liquid crystal material 13. It is su~cient that encapsulating material so at least partially separates the latter two materials, so that the switching characteristics (speed, voltage, hysteresis, etc.) of light valve 20 are generally characteristic of an encapsulating material-liquid crystal material interface and not of a matrix material-liquid crystal material interface. Preferably, encapsulating material 22 effectively separates matrix material 14 and liquid 3s crystal material 13, by which is meant that the interfaces of liquid crystal material 13 are primarily with encapsulating material 22 and not with matrix material 14.
In the foregoing figures the droplets or volumes 12 of liquid crystal material I3 have been shown as having a spherical shape as a matter of convenience and that other shapes are possible, for example oblate spheroids, s irregular shapes, or dumbbell-like shapes in which two or more droplets are connected by channels. Also, the thickness of the layer of encapsulating material 22 and the size of droplets 12 have been greatly exaggerated for clarity.
In the method of the present invention, an emulsion containing capsules io in which a volume of liquid crystal material is contained within an encapsulating material is prepared initially. (The term "capsule" should not be construed to mean necessarily spherical shapes. See the analogous discussion above in the context of the shape of the liquid crystal droplets.) An emulsion may be prepared by rapidly agitating a mixture of liquid crystal material, is encapsulating material, and a carrier medium, typically water. Optionally, an emulsifier, wetting agent, or other surface active agent may be added.
Suitable emulsification techniques are disclosed in Fergason '047, Fergason '052, Raychem '431, and Andrews et al., US 5,202,063 ( 1993).
Suitable encapsulating materials include polyvinyl alcohol), polyvinyl pyrrolidone), polyethylene glycol), poly(acrylic acid) and its copolymers, poly(hydroay acrylate), cellulose derivatives, epozies, silicones, acrylates, polyesters, styrene-acrylic acid-acrylate terpolymers, and mixtures thereof A
2s combination of as aqueous carrier medium and a encapsulating material which is soluble or colloidslly dispersible in the aqueous cancer medium is particularly preferred. Although surface active agents may be employed, it is generally preferred that the encapsulating material be capable of forming capsules containing the liquid crystal material without their addition. In such ao cases, the encapsulating material itself should have good surface active properties (i.e., be a good emulsifier). A class of polymers having such characteristics are amphiphilic polymers containing both hydrophilic and lipophilic segments. Ezamples of this class include partially hydrolyzed polyvinyl acetates) (e.g., Airvof''"' 205 from Air Products), ethylene-acrylic 3s copolymers (e.g., Adcote"", from Dow Chemical), and styrene-acrylic acid-acrylate terpolymers (e.g., Joncryf~" from S.C. Johnson).
The capsules next are separated from the carrier medium. A preferred 218 6 2 2 8 PCT~'I:S95/036~6 separation method is to centrifuge the emulsion, causing the capsules to settle to the bottom and then removing the supernatant carrier medium. Gravity settling may also be used. Yet another separation method is spray-drying, in .
which the emulsion is sprayed onto a surface and allowed to dry via evaporation s of the carrier medium. It is not necessary that the separation be complete, that is, that all the carrier medium be removed. It is only necessary that the majority of the carrier medium be removed.
The isolated capsules are dispersed in a medium comprising the matrix io material or a precursor thereof (e.g., a monomer which can be polymerized into a matrix material). The matrix material or precursor thereof is then allowed to set, to form a composite in which the matrix material is at least partially separated from the liquid crystal material by the encapsulating material. By "set," it is meant that the matrix material hardens into a continuous resinous is phase capable of containing dispersed therein plural volumes of liquid crystal material, with the intervening layer of encapsulating material. The matrix material may set by evaporation of a solvent or a carrier medium such as water or by the polymerization of a precursor monomer.
2o Suitable matrix materials include polyurethanes, polyvinyl alcohol), epoxies, polyvinyl pyrrolidone), polyethylene glycol), poly(acrylic acid) and its copolymers, poly(hydroay acrylate), cellulose derivatives, silicones, acrylates, polyesters, styrene-acrylic and-acrylate terpolymers, and mixtures thereof.
The matrix material (especially in the instance of a polyurethane) may be in latex or 2s dispersed form. Preferred matrix materials are polyurethane and styrene-acrylic acid-acrylate terpolymer (e.g., JoncrylT~ from S.C. Johnson). Blends of polymers may be used. For example a preferred matrix material is a blend of two different polyurethanes one (R96?, available from ICI Resins) selected for it high quality coating and lamination characteristics and one tR966, available ao from ICI Resins) selected for its resistance to stress clearing. Those skilled in the art will recognize from the overlap between the above lists of preferred encapsulating and matrix materials that, depending on when it is introduced in the process step, a given material may be either the encapsulating material or the matriz material.
A particularly preferred combination of encapsulating material and matrix material is polyvinyl alcohol) as the encapsulating material and poly-urethane as the matrix material. The polyvinyl alcohol) is desirable as an encapsulating _ material because is an excellent emulsion stabilizer for the liquid crystal material. Polyvinyl alcohol) stabilized emulsions can be separated into concentrated pellets without agglomeration. They can also be centrifuged for capsule size control. Polyurethane is a desirable matrix material because it is - s good for coating and lamination and has good retention of properties in high humidity. The polyvinyl alcohol)/polyurethane combination has a Iower ope-rating voltage than using polyvinyl alcohol) alone. Also, polyvinyl alcohol) is a better barrier material against environmental contaminants other than water, while polyurethane is a better barrier material against water (or water vapor).
io It can be advantageous to crosslink, physically entangle molecular chains, or otherwise ensure that the encapsulating material is fixed in place, so that displacement by the matrix material is minimized.
15 The method of this invention may be combined with the method described in U.S. Patent No. 5,585,947 of Havens et al., entitled "Liquid Crystal Composite and Method of Making," to make novel composites. Devices made with a combination of these methods can exhibit wider operating temperature ranges, better coatings with 2o high liquid crystal loadings, low operating voltages, good voltage-holding performance, and can provide these benefits all in a single device.
In the above discussions, particular those with reference to Wig. la-b and 2s Wig. 2a-b, have been in the contest of nematic liquid crystals having a positive dielectric anisotropy, other types of liquid crystals may be encapsulated by the method of this invention. One may apply the techniques of this invention to liquid crystal composites in which the liquid crystal material is a chiral nematic (also known as cholesteric) one, such as disclosed in Crooker et al., US
5,200,845 30 (1993) and U.S. Patent No. 5,463,482 to Jones.
The practice of this invention may be further understood by reference to 35 the following examples, which are provided by way of illustration and not of limitation. All relative amounts are in parts by weight, unless specified otherwise.
-?-WO 95/25778 2 i 8 6 2 2 8 PCT;2~S9~i03656 Capsules of liquid crystal material 1005 (from Chisso) contained in AirvolT"' 205 PVA (from Air Products) and having a volume median diameter of 2.48 ~tm were prepared and separated from the carrier medium by s centrifugation at 13,500 rpm for 35 min to form a pellet of the capsules.
The supernatant was drained off, and the pellet was dispersed in 6°!o PVA
solution.
This centrifugation process was repeated 15 times in order to narrow the droplet size distribution of the liquid crystal-containing emulsion. The resulting pellet was separated into portions, one of which was re-dispersed into a solution of io PVA, the other was re-dispersed into Neo-rezTM polyurethane latex (ICI
R,esins), leading to emulsions with an 83:17 liquid crystal to (encapsulating-plus-matrix material) ratio and 609'o solids.
Coatings onto ITO-glass were made which were between 5 and 8 ~m is thick. The samples with the NeorezT'~ polyurethane matrix operated at 25°!0 lower field (Egp =1.8 voltl~tm for the NeorezTM devices and 2.4 volt/~tm for the PVA devices). It should be noted that without centrifugation the field needed to operate the devices would be significantly higher than 2.4 V/Etm, and that centrifugation for droplet size control does not work well for Neorez stabilized LC
2o emulsions.
Into a vial was weighed 16.0 g of liquid crystal TL205 (EM Industries), 3.1373 g of acryiate mixture PN393 (EM Industries) and 0.062? of 1,1,1-trimethyl-olpropane trimethacrylate (Polysciences). This mizture was stirred until clear, 25 then 18.1115 g of it was added into a beaker. To this beaker was added 20.12 g of a 9b w/w aqueous solution of PVA (AirvolTM 205) and 12.08 g of water. This mixture was mixed to yield an emulsion with a mean volume diameter of 1.91 ~m as determined by Coulter counter. The emulsion was degassed overnight. The emulsion was divided into 5 batches, each of which was cooled 3o with stirring for 30 min at 2-4 °C, then cured with a UV light source at 12 mW/cm2 for 5 min. The portions were remised, poured into a centrifuge tube and centrifuged for a total of 70 min. The supernatant was decanted leaving a pellet of centrifuged emulsion at the base of the tube. The pellet was determined to have 23 96 water by drying a portion of the pellet overnight at 60 °C. Into a vial ss was added 1.1081 g of pellet and 1.1087 g of a 6.25 96 w/w aqueous solution of PVA
(AirvolTM 205). The mixture was stirred gently with a spatula and filtered _g_ «
O 9Si257 i$
218 6 2 2 8 PCT~~' S95~036~6 through a 5.0 ~m membrane. In a laminar flow hood, the emulsion was coated onto an ITO-coated glass substrate with a doctor blade with a 2 mil (0.005 cm) gap. The film was allowed to dry for 45 min. A second ITO-glass substrate was laminated on top of the coating on an 85 °C hot plate. Three devices made in this s manner were determined to have thicknesses of 6.98 Vim, 6.67 ~.im, and 6.00 dun by interference measurements. The procedure described above was repeated, except the pellets were worked up in aqueous solutions of Neorez 8,967 polyurethane and JoncrylTM 74 styrene-acrylic acid-acrylate terpolymer, res-pectively. The devices with each of these three matriac materials were tested io electro-optically at temperatures from 5 °C to 55 °C. The results of these tests are shown in the attached graphs. The data plotted in Fig. 3 show the contrast ratio divided by thickness (CRlt) measured at f/3.5 at a number of temperatures for the devices described above. It is desirable to have a high value of CRJt, and it is desirable to have a high value over a wide temperature range. The data show is that when the matrix material is PVA, the CRlt becomes very low at 15 °C, making the composite less desirable for use in a display. By changing the matrix material to Neorez'''"~ polyurethane, the CRJt at 15 °C is above 2 at 15 °C, and by changing to Joncryl''b' terpolymer, the CRlt is still above 1.5 at 5 °C.
2o The data in Fig. 4 show the field needed to turn the above devices on to 90 9b (Egp) of the final transmittance. It is desirable to have a low value of Egp.
Note that for the devises with PVA as the matrix material, the E9a rises at low temperatures, whereas for the other two materials, the Egp remains low at low temperature. These characteristics make the devices with the different matrix 25 materials useful over a wider temperature range than when the same polymer (PVA) is used throughout. Other benefits of having ~leorezT"' or Joncryf'~"~
as the matrix materials are that the coatings from the emulsions containing these two polymers were of significantly better quality (fewer defects), and lamination of ITO-glass was easier than for the devices using PVA only.
Into a small beaker was weighed 10.0 g of RY -1005 liquid crystal (Chisso) and 27.32 g of Adcote'''"~ 50T4983 ethylene acrylic acid latex (Morton Thiokol).
The components were mixed for 10 min at 10,000 rpm to yield an emulsion with a volume median droplet size of 2.7 ~tm. The emulsion was diluted by adding 16.0 g of a 696 aqueous Adcote solution to 15.443 g of emulsion. The diluted emulsion was then centrifuged at 10,000 rpm for 60 min. The supernatant PCT~'L'S9~/0365G
"° 9v''''g 218 6 2 2 8 solution was decanted and a pellet weighing 6.45 g was recovered. A portion of the pellet (2.93 g) was mixed with a 20 % solution of 5.73 g of AirvolTM 205 polyvinyl alcohol) (Air Products). Another portion of the pellet (2.40 g) was put back into Adcote by mixing with 3.85 g of a 6 % aqueous Adcote solution.
s Devices were made from each of these emulsions by coating them onto ITO
coated polyester film, drying, and laminating a second piece of ITO polyester film. The electro-optical properties of the devices were compared to each other and to a device made from poly(vinyi alcohol) alone. The composite device in which the encapsulating polymer was Adcote and the matrix polymer was io poly(vinyl alcohol) had lower field of operation (5.7 V/pm) than the device made from all Adcote (7.5 V/~tm), and faster switching speeds (1 cosec rise, 3 cosec fall) than the device from all polyvinyl alcohol) (58 cosec rise, 29 cosec fall).
The foregoing detailed description of the invention includes passages is which are chiefly or exclusively concerned with particular parts or aspects of the invention. It is to be understood that this is for clarity and convenience, that a particular feature may be relevant in more than just passage in which it is disclosed, and that the disclosure herein includes all the appropriate com-binations of information found in the different passages. Similarly, although 2o the various figures and descriptions thereof relate to specific embodiments of the invention, it is to be understood that where a specific feature is disclosed in the oonteat of a particular figure, such feature can also be used, to the extent appropriate, in the oonteat of another figure, in combination with another feature, or in the invention in general.
Fig. 2a-2b (where numerals repeated from Fig. la-b denote like elements) show a light valve 20 of this invention in which this objective is achieved.
Light valve 20 comprises a liquid crystal composite 21 which is similar to composite s of Fig. la-b, except that liquid crystal material 13 is separated from matrix material 14 by an encapsulating material 22. Light valve 20 appears frosty or translucent in the off state (Fig. 2a) and transparent in the on-state (Fig.
2b), for the reasons given above. The surface interactions affecting the alignment of liquid crystal material 13 are predominantly with encapsulating material 22 io and not with matrix material 14. Encapsulating material 22 may be selected on the basis of its interactions with liquid crystal material 13, while matrix material 14 may be selected on the basis of its mechanical, optical, or other properties. This way, the necessity to compromise in respect of one set or another of properties is avoided.
is Matching of n~ of the liquid crystal material with the index of refraction of the encapsulating material is important only if the thickness of the layer of encapsulating material is comparable to the wavelength of light. Generally the thickness is less than approaimatxly 100 nm, much less than the wavelengths of 20 400 to 700 nm for visible light, so that the matching of the indices of refraction is normally not necessary. However, where the layer of encapsulating material is thick or where minimizing of on-state haze is an objective (e.g., in window applications), matching of the indices of refraction is desirable. A colored visual effect may be obtained by inclusion of dyes, either pleochroic or isotropic, in the 25 liquid crystal material, In order to obtain the advantages of the present invention, it is not necessary that encapsulating material 22 completely separates matrix material 14 from liquid crystal material 13. It is su~cient that encapsulating material so at least partially separates the latter two materials, so that the switching characteristics (speed, voltage, hysteresis, etc.) of light valve 20 are generally characteristic of an encapsulating material-liquid crystal material interface and not of a matrix material-liquid crystal material interface. Preferably, encapsulating material 22 effectively separates matrix material 14 and liquid 3s crystal material 13, by which is meant that the interfaces of liquid crystal material 13 are primarily with encapsulating material 22 and not with matrix material 14.
In the foregoing figures the droplets or volumes 12 of liquid crystal material I3 have been shown as having a spherical shape as a matter of convenience and that other shapes are possible, for example oblate spheroids, s irregular shapes, or dumbbell-like shapes in which two or more droplets are connected by channels. Also, the thickness of the layer of encapsulating material 22 and the size of droplets 12 have been greatly exaggerated for clarity.
In the method of the present invention, an emulsion containing capsules io in which a volume of liquid crystal material is contained within an encapsulating material is prepared initially. (The term "capsule" should not be construed to mean necessarily spherical shapes. See the analogous discussion above in the context of the shape of the liquid crystal droplets.) An emulsion may be prepared by rapidly agitating a mixture of liquid crystal material, is encapsulating material, and a carrier medium, typically water. Optionally, an emulsifier, wetting agent, or other surface active agent may be added.
Suitable emulsification techniques are disclosed in Fergason '047, Fergason '052, Raychem '431, and Andrews et al., US 5,202,063 ( 1993).
Suitable encapsulating materials include polyvinyl alcohol), polyvinyl pyrrolidone), polyethylene glycol), poly(acrylic acid) and its copolymers, poly(hydroay acrylate), cellulose derivatives, epozies, silicones, acrylates, polyesters, styrene-acrylic acid-acrylate terpolymers, and mixtures thereof A
2s combination of as aqueous carrier medium and a encapsulating material which is soluble or colloidslly dispersible in the aqueous cancer medium is particularly preferred. Although surface active agents may be employed, it is generally preferred that the encapsulating material be capable of forming capsules containing the liquid crystal material without their addition. In such ao cases, the encapsulating material itself should have good surface active properties (i.e., be a good emulsifier). A class of polymers having such characteristics are amphiphilic polymers containing both hydrophilic and lipophilic segments. Ezamples of this class include partially hydrolyzed polyvinyl acetates) (e.g., Airvof''"' 205 from Air Products), ethylene-acrylic 3s copolymers (e.g., Adcote"", from Dow Chemical), and styrene-acrylic acid-acrylate terpolymers (e.g., Joncryf~" from S.C. Johnson).
The capsules next are separated from the carrier medium. A preferred 218 6 2 2 8 PCT~'I:S95/036~6 separation method is to centrifuge the emulsion, causing the capsules to settle to the bottom and then removing the supernatant carrier medium. Gravity settling may also be used. Yet another separation method is spray-drying, in .
which the emulsion is sprayed onto a surface and allowed to dry via evaporation s of the carrier medium. It is not necessary that the separation be complete, that is, that all the carrier medium be removed. It is only necessary that the majority of the carrier medium be removed.
The isolated capsules are dispersed in a medium comprising the matrix io material or a precursor thereof (e.g., a monomer which can be polymerized into a matrix material). The matrix material or precursor thereof is then allowed to set, to form a composite in which the matrix material is at least partially separated from the liquid crystal material by the encapsulating material. By "set," it is meant that the matrix material hardens into a continuous resinous is phase capable of containing dispersed therein plural volumes of liquid crystal material, with the intervening layer of encapsulating material. The matrix material may set by evaporation of a solvent or a carrier medium such as water or by the polymerization of a precursor monomer.
2o Suitable matrix materials include polyurethanes, polyvinyl alcohol), epoxies, polyvinyl pyrrolidone), polyethylene glycol), poly(acrylic acid) and its copolymers, poly(hydroay acrylate), cellulose derivatives, silicones, acrylates, polyesters, styrene-acrylic and-acrylate terpolymers, and mixtures thereof.
The matrix material (especially in the instance of a polyurethane) may be in latex or 2s dispersed form. Preferred matrix materials are polyurethane and styrene-acrylic acid-acrylate terpolymer (e.g., JoncrylT~ from S.C. Johnson). Blends of polymers may be used. For example a preferred matrix material is a blend of two different polyurethanes one (R96?, available from ICI Resins) selected for it high quality coating and lamination characteristics and one tR966, available ao from ICI Resins) selected for its resistance to stress clearing. Those skilled in the art will recognize from the overlap between the above lists of preferred encapsulating and matrix materials that, depending on when it is introduced in the process step, a given material may be either the encapsulating material or the matriz material.
A particularly preferred combination of encapsulating material and matrix material is polyvinyl alcohol) as the encapsulating material and poly-urethane as the matrix material. The polyvinyl alcohol) is desirable as an encapsulating _ material because is an excellent emulsion stabilizer for the liquid crystal material. Polyvinyl alcohol) stabilized emulsions can be separated into concentrated pellets without agglomeration. They can also be centrifuged for capsule size control. Polyurethane is a desirable matrix material because it is - s good for coating and lamination and has good retention of properties in high humidity. The polyvinyl alcohol)/polyurethane combination has a Iower ope-rating voltage than using polyvinyl alcohol) alone. Also, polyvinyl alcohol) is a better barrier material against environmental contaminants other than water, while polyurethane is a better barrier material against water (or water vapor).
io It can be advantageous to crosslink, physically entangle molecular chains, or otherwise ensure that the encapsulating material is fixed in place, so that displacement by the matrix material is minimized.
15 The method of this invention may be combined with the method described in U.S. Patent No. 5,585,947 of Havens et al., entitled "Liquid Crystal Composite and Method of Making," to make novel composites. Devices made with a combination of these methods can exhibit wider operating temperature ranges, better coatings with 2o high liquid crystal loadings, low operating voltages, good voltage-holding performance, and can provide these benefits all in a single device.
In the above discussions, particular those with reference to Wig. la-b and 2s Wig. 2a-b, have been in the contest of nematic liquid crystals having a positive dielectric anisotropy, other types of liquid crystals may be encapsulated by the method of this invention. One may apply the techniques of this invention to liquid crystal composites in which the liquid crystal material is a chiral nematic (also known as cholesteric) one, such as disclosed in Crooker et al., US
5,200,845 30 (1993) and U.S. Patent No. 5,463,482 to Jones.
The practice of this invention may be further understood by reference to 35 the following examples, which are provided by way of illustration and not of limitation. All relative amounts are in parts by weight, unless specified otherwise.
-?-WO 95/25778 2 i 8 6 2 2 8 PCT;2~S9~i03656 Capsules of liquid crystal material 1005 (from Chisso) contained in AirvolT"' 205 PVA (from Air Products) and having a volume median diameter of 2.48 ~tm were prepared and separated from the carrier medium by s centrifugation at 13,500 rpm for 35 min to form a pellet of the capsules.
The supernatant was drained off, and the pellet was dispersed in 6°!o PVA
solution.
This centrifugation process was repeated 15 times in order to narrow the droplet size distribution of the liquid crystal-containing emulsion. The resulting pellet was separated into portions, one of which was re-dispersed into a solution of io PVA, the other was re-dispersed into Neo-rezTM polyurethane latex (ICI
R,esins), leading to emulsions with an 83:17 liquid crystal to (encapsulating-plus-matrix material) ratio and 609'o solids.
Coatings onto ITO-glass were made which were between 5 and 8 ~m is thick. The samples with the NeorezT'~ polyurethane matrix operated at 25°!0 lower field (Egp =1.8 voltl~tm for the NeorezTM devices and 2.4 volt/~tm for the PVA devices). It should be noted that without centrifugation the field needed to operate the devices would be significantly higher than 2.4 V/Etm, and that centrifugation for droplet size control does not work well for Neorez stabilized LC
2o emulsions.
Into a vial was weighed 16.0 g of liquid crystal TL205 (EM Industries), 3.1373 g of acryiate mixture PN393 (EM Industries) and 0.062? of 1,1,1-trimethyl-olpropane trimethacrylate (Polysciences). This mizture was stirred until clear, 25 then 18.1115 g of it was added into a beaker. To this beaker was added 20.12 g of a 9b w/w aqueous solution of PVA (AirvolTM 205) and 12.08 g of water. This mixture was mixed to yield an emulsion with a mean volume diameter of 1.91 ~m as determined by Coulter counter. The emulsion was degassed overnight. The emulsion was divided into 5 batches, each of which was cooled 3o with stirring for 30 min at 2-4 °C, then cured with a UV light source at 12 mW/cm2 for 5 min. The portions were remised, poured into a centrifuge tube and centrifuged for a total of 70 min. The supernatant was decanted leaving a pellet of centrifuged emulsion at the base of the tube. The pellet was determined to have 23 96 water by drying a portion of the pellet overnight at 60 °C. Into a vial ss was added 1.1081 g of pellet and 1.1087 g of a 6.25 96 w/w aqueous solution of PVA
(AirvolTM 205). The mixture was stirred gently with a spatula and filtered _g_ «
O 9Si257 i$
218 6 2 2 8 PCT~~' S95~036~6 through a 5.0 ~m membrane. In a laminar flow hood, the emulsion was coated onto an ITO-coated glass substrate with a doctor blade with a 2 mil (0.005 cm) gap. The film was allowed to dry for 45 min. A second ITO-glass substrate was laminated on top of the coating on an 85 °C hot plate. Three devices made in this s manner were determined to have thicknesses of 6.98 Vim, 6.67 ~.im, and 6.00 dun by interference measurements. The procedure described above was repeated, except the pellets were worked up in aqueous solutions of Neorez 8,967 polyurethane and JoncrylTM 74 styrene-acrylic acid-acrylate terpolymer, res-pectively. The devices with each of these three matriac materials were tested io electro-optically at temperatures from 5 °C to 55 °C. The results of these tests are shown in the attached graphs. The data plotted in Fig. 3 show the contrast ratio divided by thickness (CRlt) measured at f/3.5 at a number of temperatures for the devices described above. It is desirable to have a high value of CRJt, and it is desirable to have a high value over a wide temperature range. The data show is that when the matrix material is PVA, the CRlt becomes very low at 15 °C, making the composite less desirable for use in a display. By changing the matrix material to Neorez'''"~ polyurethane, the CRJt at 15 °C is above 2 at 15 °C, and by changing to Joncryl''b' terpolymer, the CRlt is still above 1.5 at 5 °C.
2o The data in Fig. 4 show the field needed to turn the above devices on to 90 9b (Egp) of the final transmittance. It is desirable to have a low value of Egp.
Note that for the devises with PVA as the matrix material, the E9a rises at low temperatures, whereas for the other two materials, the Egp remains low at low temperature. These characteristics make the devices with the different matrix 25 materials useful over a wider temperature range than when the same polymer (PVA) is used throughout. Other benefits of having ~leorezT"' or Joncryf'~"~
as the matrix materials are that the coatings from the emulsions containing these two polymers were of significantly better quality (fewer defects), and lamination of ITO-glass was easier than for the devices using PVA only.
Into a small beaker was weighed 10.0 g of RY -1005 liquid crystal (Chisso) and 27.32 g of Adcote'''"~ 50T4983 ethylene acrylic acid latex (Morton Thiokol).
The components were mixed for 10 min at 10,000 rpm to yield an emulsion with a volume median droplet size of 2.7 ~tm. The emulsion was diluted by adding 16.0 g of a 696 aqueous Adcote solution to 15.443 g of emulsion. The diluted emulsion was then centrifuged at 10,000 rpm for 60 min. The supernatant PCT~'L'S9~/0365G
"° 9v''''g 218 6 2 2 8 solution was decanted and a pellet weighing 6.45 g was recovered. A portion of the pellet (2.93 g) was mixed with a 20 % solution of 5.73 g of AirvolTM 205 polyvinyl alcohol) (Air Products). Another portion of the pellet (2.40 g) was put back into Adcote by mixing with 3.85 g of a 6 % aqueous Adcote solution.
s Devices were made from each of these emulsions by coating them onto ITO
coated polyester film, drying, and laminating a second piece of ITO polyester film. The electro-optical properties of the devices were compared to each other and to a device made from poly(vinyi alcohol) alone. The composite device in which the encapsulating polymer was Adcote and the matrix polymer was io poly(vinyl alcohol) had lower field of operation (5.7 V/pm) than the device made from all Adcote (7.5 V/~tm), and faster switching speeds (1 cosec rise, 3 cosec fall) than the device from all polyvinyl alcohol) (58 cosec rise, 29 cosec fall).
The foregoing detailed description of the invention includes passages is which are chiefly or exclusively concerned with particular parts or aspects of the invention. It is to be understood that this is for clarity and convenience, that a particular feature may be relevant in more than just passage in which it is disclosed, and that the disclosure herein includes all the appropriate com-binations of information found in the different passages. Similarly, although 2o the various figures and descriptions thereof relate to specific embodiments of the invention, it is to be understood that where a specific feature is disclosed in the oonteat of a particular figure, such feature can also be used, to the extent appropriate, in the oonteat of another figure, in combination with another feature, or in the invention in general.
Claims (12)
1. A method for making a liquid crystal composite wherein plural volumes of a liquid crystal material are dispersed in a matrix material and the liquid crystal material is at least partially separated from the matrix material by an encapsulating material disposed therebetween, which method comprises the steps of:
(a) emulsifying a combination of the liquid crystal material, the encapsulating material, and a carrier medium to form an emulsion in which capsules comprising a volume of liquid crystal material contained within the encapsulating material are suspended in the carrier medium;
(b) separating the capsules from the carrier medium;
(c) dispersing the capsules in a medium in which the matrix material or a precursor thereof is present; and (d) causing the matrix material or precursor thereof to set around the capsules, to form the liquid crystal composite.
(a) emulsifying a combination of the liquid crystal material, the encapsulating material, and a carrier medium to form an emulsion in which capsules comprising a volume of liquid crystal material contained within the encapsulating material are suspended in the carrier medium;
(b) separating the capsules from the carrier medium;
(c) dispersing the capsules in a medium in which the matrix material or a precursor thereof is present; and (d) causing the matrix material or precursor thereof to set around the capsules, to form the liquid crystal composite.
2. A method according to claim 1, wherein the capsules are separated from the carrier medium by centrifugation.
3. A method according to claim 1 or 2, wherein the liquid crystal material is a nematic liquid crystal material having positive dielectric anisotropy.
4. A method according to claim 3, wherein the index of refraction of the matrix material is substantially the same as the ordinary index of refraction of the liquid crystal material.
5. A method according to claim 3 or 4, wherein the index of refraction of the encapsulating material is substantially the same as the ordinary index of refraction of the liquid crystal material.
6. A method according to claim 3, wherein the index of refraction of the encapsulating and matrix materials and the ordinary index of refraction of the liquid crystal material are substantially the same.
7. A method according to claim 1 or 2, wherein the liquid crystal material is a chiral nematic liquid crystal material.
8. A method according to any one of claims 1 to 7, wherein the encapsulating material is selected from the group consisting of polyvinyl alcohol), polyvinyl pyrrolidone), polyethylene glycol), poly(acrylic acid) and its copolymers, poly(hydroxy acrylate), cellulose derivatives, epoxies, silicones, acrylates, polyesters, styrene-acrylic acid-acrylate terpolymers, and mixtures thereof.
9. A method according to any one of the claims 1 to 8, wherein the matrix material is selected from the group consisting of polyurethanes, polyvinyl alcohol), polyvinyl pyrrolidone), polyethylene glycol), poly(acrylic acid) and its copolymers, poly(hydroxy acrylate), cellulose derivatives, epoxies, silicones, acrylates, polyesters, styrene-acrylic acid-acrylate terpolymers, and mixtures thereof.
10. A method according to any one of claims 1 to 7, wherein the encapsulating material is a polyvinyl alcohol) and the matrix material is a polyurethane.
11. A method according to any one of the claims 1 to 10, wherein the liquid crystal material comprises a pleochroic dye.
12. A method according to any one of the claims 1 to 11, wherein the encapsulating material is fixed in place by crosslinking or physical entanglement of molecular chains.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/217,581 | 1994-03-24 | ||
| US08/217,581 US5405551A (en) | 1994-03-24 | 1994-03-24 | Method of making liquid crystal composite |
| PCT/US1995/003656 WO1995025778A1 (en) | 1994-03-24 | 1995-03-22 | Method of making liquid crystal composite |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2186228A1 CA2186228A1 (en) | 1995-09-28 |
| CA2186228C true CA2186228C (en) | 2005-10-18 |
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| Application Number | Title | Priority Date | Filing Date |
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| CA002186228A Expired - Lifetime CA2186228C (en) | 1994-03-24 | 1995-03-22 | Method of making liquid crystal composite |
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| US (1) | US5405551A (en) |
| EP (1) | EP0751982B1 (en) |
| JP (1) | JP3583135B2 (en) |
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| CA (1) | CA2186228C (en) |
| DE (1) | DE69520139T2 (en) |
| HK (1) | HK1011703A1 (en) |
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| JP3078623B2 (en) * | 1991-09-21 | 2000-08-21 | 株式会社半導体エネルギー研究所 | Liquid crystal electro-optical device and manufacturing method thereof |
| US5585947A (en) * | 1994-03-24 | 1996-12-17 | Raychem Corporation | Method of making liquid crystal composite which has interfacial material disposed between liquid crystal and encapsulating medium |
| JPH0815676A (en) * | 1994-06-30 | 1996-01-19 | Japan Gore Tex Inc | Optical liquid crystal member |
| US5543944A (en) * | 1994-10-31 | 1996-08-06 | Raychem Corporation | Method of imbibing a component into a liquid crystal composite |
| WO1996019547A1 (en) * | 1994-12-21 | 1996-06-27 | Raychem Corporation | Method of making liquid crystal composite |
| CA2209685C (en) * | 1995-01-05 | 2007-12-18 | Raychem Corporation | Method of making a liquid crystal composite including a dye |
| US5835174A (en) * | 1995-10-12 | 1998-11-10 | Rohm And Haas Company | Droplets and particles containing liquid crystal and films and apparatus containing the same |
| US6271898B1 (en) | 1996-09-19 | 2001-08-07 | Rohm And Haas Company | Particles and droplets containing liquid domains and method for forming in an aqueous medium |
| KR100218986B1 (en) * | 1995-12-27 | 1999-09-01 | 니시무로 타이죠 | Liquid crystal display device and its manufacture method |
| US5695594A (en) * | 1996-01-05 | 1997-12-09 | Raychem Corporation | Method of making a liquid crystal light valve |
| US6174467B1 (en) | 1997-03-28 | 2001-01-16 | Ying Yen Hsu | Microencapsulated liquid crystal and method |
| US6203723B1 (en) | 1998-03-12 | 2001-03-20 | Ying Yen Hsu | Microencapsulated liquid crystal having multidomains induced by the polymer network and method |
| US6067143A (en) * | 1998-06-04 | 2000-05-23 | Tomita; Akira | High contrast micro display with off-axis illumination |
| US6246459B1 (en) | 1998-06-10 | 2001-06-12 | Tyco Electronics Corporation | Assembly including an active matrix liquid crystal display module and having plural environmental seals |
| US6297789B2 (en) | 1998-07-09 | 2001-10-02 | Tyco Electronics Corporation | Integrated circuit card with liquid crystal display for viewing at least a portion of the information stored in the card |
| JP4846711B2 (en) * | 2004-04-08 | 2011-12-28 | フォトン・ダイナミクス・インコーポレーテッド | Polymer-dispersed liquid crystal formulation for modulator manufacturing |
| JP2009218711A (en) * | 2008-03-07 | 2009-09-24 | Canon Inc | Information processor, image processor, control method of information processor, control method of image processor and program |
| TWI395017B (en) * | 2008-12-15 | 2013-05-01 | Ind Tech Res Inst | Reworkable liquid crystal film and its manufacturing method |
| US8801964B2 (en) | 2010-12-22 | 2014-08-12 | Photon Dynamics, Inc. | Encapsulated polymer network liquid crystal material, device and applications |
| KR101356851B1 (en) | 2012-04-23 | 2014-01-29 | 호서대학교 산학협력단 | Fabrication Methods of Liquid Crystal Capsules with Powder Type |
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| US4435047A (en) * | 1981-09-16 | 1984-03-06 | Manchester R & D Partnership | Encapsulated liquid crystal and method |
| AU4117585A (en) * | 1984-03-19 | 1985-10-11 | Kent State University | Light modulating material comprising a liquid crystal dispersion in a synthetic resin matrix |
| US4992201A (en) * | 1984-03-20 | 1991-02-12 | Taliq Corporation | Latex entrapped ncap liquid crystal composition, method and apparatus |
| US4643528A (en) * | 1985-03-18 | 1987-02-17 | Manchester R & D Partnership | Encapsulated liquid crystal and filler material |
| US5216530A (en) * | 1985-06-03 | 1993-06-01 | Taliq Corporation | Encapsulated liquid crystal having a smectic phase |
| US5018840A (en) * | 1985-07-31 | 1991-05-28 | Matsushita Electric Industrial Co., Ltd. | Image display device having a photosetting binder |
| DE3752026T2 (en) * | 1986-12-23 | 1997-06-26 | Asahi Glass Co Ltd | Optical liquid crystal device and method for its manufacture. |
| US4818070A (en) * | 1987-01-22 | 1989-04-04 | Asahi Glass Company Ltd. | Liquid crystal optical device using U.V.-cured polymer dispersions and process for its production |
| CA1307576C (en) * | 1987-10-20 | 1992-09-15 | Yoshi Arai | Liquid crystal devices and process for producing the same |
| JPH01203494A (en) * | 1988-02-08 | 1989-08-16 | Fuji Photo Film Co Ltd | Liquid crystal display element |
| US4950052A (en) * | 1988-08-29 | 1990-08-21 | Taliq Corporation | Encapsulated liquid crystal apparatus with a polymer additive |
| US5206747A (en) * | 1988-09-28 | 1993-04-27 | Taliq Corporation | Polymer dispersed liquid crystal display with birefringence of the liquid crystal at least 0.23 |
| EP0421240B1 (en) * | 1989-09-26 | 1996-01-31 | Sumitomo Electric Industries, Ltd. | Liquid crystal display element |
| JPH03288823A (en) * | 1990-04-05 | 1991-12-19 | Seiko Epson Corp | Liquid crystal electrooptical element |
| JPH047518A (en) * | 1990-04-25 | 1992-01-10 | Seiko Epson Corp | Liquid crystal electrooptical element |
| JPH04140718A (en) * | 1990-10-01 | 1992-05-14 | Semiconductor Energy Lab Co Ltd | Liquid crystal device |
| JP2992648B2 (en) * | 1990-12-20 | 1999-12-20 | 株式会社半導体エネルギー研究所 | Method for manufacturing liquid crystal electro-optical device |
| JPH04240614A (en) * | 1991-01-24 | 1992-08-27 | Seiko Epson Corp | Liquid crystal electrooptical element |
| WO1992014184A1 (en) * | 1991-02-11 | 1992-08-20 | Raychem Corporation | Method for making encapsulated liquid crystal material |
| EP0725941A1 (en) * | 1992-03-10 | 1996-08-14 | Raychem Corporation | Encapsulated liquid crystal structures, apparatus containing the same, and methods therefor |
| JP3142961B2 (en) * | 1992-06-23 | 2001-03-07 | 株式会社リコー | Liquid crystal display |
| US5335101A (en) * | 1993-05-06 | 1994-08-02 | Raychem Corporation | Method of making liquid crystal material including polymerizing dispersion of prepolymer and liquid crystal which is immiscible in the prepolymer |
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- 1994-03-24 US US08/217,581 patent/US5405551A/en not_active Expired - Lifetime
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1995
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- 1995-03-22 DE DE69520139T patent/DE69520139T2/en not_active Expired - Lifetime
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- 1995-03-22 JP JP52482195A patent/JP3583135B2/en not_active Expired - Lifetime
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- 1995-03-22 EP EP95914837A patent/EP0751982B1/en not_active Expired - Lifetime
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1998
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| EP0751982B1 (en) | 2001-02-21 |
| JPH09510746A (en) | 1997-10-28 |
| HK1011703A1 (en) | 1999-07-16 |
| CA2186228A1 (en) | 1995-09-28 |
| WO1995025778A1 (en) | 1995-09-28 |
| MX9604250A (en) | 1998-05-31 |
| DE69520139D1 (en) | 2001-03-29 |
| KR100370283B1 (en) | 2003-04-08 |
| DE69520139T2 (en) | 2001-09-27 |
| JP3583135B2 (en) | 2004-10-27 |
| EP0751982A1 (en) | 1997-01-08 |
| US5405551A (en) | 1995-04-11 |
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